2007/01/25 by Hal Berenson, Phil Bernstein, Jim Gray +3 · 2 citations
Computer Science · #cs.DB
published as Proc. ACM SIGMOD 95, pp. 1-10, San Jose CA, June 1995
arxiv created 2007/01/25 · arxiv updated 2009/12/01
ANSI SQL-92 defines Isolation Levels in terms of phenomena: Dirty Reads, Non-Repeatable Reads, and Phantoms. This paper shows that these phenomena and the ANSI SQL definitions fail to characterize several popular isolation levels, including the standard locking implementations of the levels. Investigating the ambiguities of the phenomena leads to clearer definitions; in addition new phenomena that better characterize isolation types are introduced. An important multiversion isolation type, Snapshot Isolation, is defined.